Ion exchange catalysts for the preparation of bisphenols

ABSTRACT

Modification of an insoluble strong-acid cation-exchange resin in acid form by partial neutralization with a thiazolidine yields an improved catalyst for the preparation of bisphenols by condensation of a phenol and a ketone.

United States atent 11 1 Gammill et al.

ION EXCHANGE CATALYSTS FOR THE PREPARATION OF BISPIIENOLS The Dow Chemical Company, Midland, Mich.

Filed: June 28, 1971 Appl. No.: 157,721

Related US. Application Data Division of Ser. No. 17,291, March 6, i970, Pat. No. 3,634,341.

Assignee:

U.S. Cl 260/619 A Int. Cl. C07c 39/16, C07c 37/00 Field of Search 260/619 A 1 Sept. 18, 1973 [56] References Cited UNITED STATES PATENTS 3,049,569 8/1962 Apel et al. 260 619 A 3,153,001 10/1964 Apel et al. 260/619 A x 3,049,568 8/1962 Apel et al. 260/619 A 3,242,220 3/1966 Apel et al. 2601619 A 3,242,219 3/1966 Apel et al. 260/619 A Primary Examiner-Leon Zitver Assistant ExaminerNorman Morgenstern Attorney-Griswold and Burdick 4 Claims, No Drawings 3 our prior U.S. application Ser. No. 17,291, filed Mar.

6, 1970, now U.S. Pat. No. 3,634,341.

BACKGROUND OF THE INVENTION Certain sulfur compounds have long been recognized as effective promoters for the acid catalyzed condensation of phenols and ketones to form bisphenols. For example, in U. S. Pat. No. 2,359,242 Perkins and Bryner describe the use of H 8 in the condensation of phenol with acetone methyl ethyl ketone, cyclohexanone, and other similar ketones. In U. S. Pat. No. 2,917,550 Dietzler recommends as a promoter a soluble sulfur compound such as I-I S, methyl mercaptan, ethyl mercaptan or N-octyl mercapton. Such soluble promoters, however, introduce subsequent problems in the purification of the bisphenol.

McNutt and Gammill in U. S. Pat. No. 3,394,089 teach a method of modifying insoluble strong-acid cation-exchange resins in the acid form by partial neutralization with a mercaptoamine. The modification of the strong-acid cation-exchange resin was shown to give an improved strong acid catalyst for the preparation of bisphenols. In spite of this improvement, still better catalysts have been sought to lessen the amounts of undesirable impurities formed, give a product of higher purity and shorten the induction time before acceptable product can be obtained.

SUMMARY OF THE INVENTION The present invention is a new catalyst prepared by partially neutralizing an insoluble strong acid cation exchange resin in the acid form with a thiazolidine having the general formula R, CIt N bon atoms.

These new catalysts improve the preparation of bisphenols by the condensation of a phenol with a ketone by increasing the efficiency of the strong-acid resin, shortening the induction time and lessening product conrumination.

The improved catalyst of the present invention can be prepared using any insoluble strong-acid cationexchange resin. Particularly suitable are aromatic sulfonic acid resins having a cation-exchange capacity of at least 0.5 and advantageously 2.0 or more meq./g. dry

weight. Commercial strong-acid resins prepared by the sulfonation of a styrene-divinyl-benzene resin, as described for example, by Bodamer in U. S. Pat. No. 2,597,438, by Wheaton and Harrington in U. S. Pat.

No. 2,642,4l7 or Bortnick in U. S. Pat. No. 3,037,052, are most satisfactory. Such commercial sulfonic acid resins as Dowex 50 resin, Amberlite lRl 20 resin, Amberlite 200 resin and Duolite C-20 resin, which normally have an exchange capacity of 4.2-5.2 meq./g. dry weight, make superior resin catalysts after partial neutralization.

The thiazolidines of the present invention may suitably be any of those described by the general formula above. These thiazolidines may be simply prepared by the reaction of a ketone or aldehyde, an aziridine compound and H 8 as described by Bestian in Ann. 566, 210 (1950). Typical examples of suitable thiazolidines include: thiazolidine; 2-alkyl and cycloalkyl thiazolidines, such as 2,2-dimethyl-, 2-methyl-2-ethyl-, 2-methyl-2-isobutyl-, 2-octyl-, 2-propyl-2-nonyland 2-cyclohexylthiazolidine; Z-phenalkyl, phenyl or alkylphenyl thiazolidines, such as 2-methyl-2-phenyl-, 2-ptolyland Z-phenethylthiazolidine; 2,2-alkylene thiazolidines such as 2,2-pentamethylene and 2,2 hexamethylenethiazolidine; 3-alkyl, hydroxyalkyl, cyanoalkyl, aminoalkyl and cycloalkylthiazolidines, such as 3- methyl-, 3-decyl-, 3-cyanoethyl, 3-aminopropyl, 3- hydroxyethyl and 3-cyclohexylthiazolidine; 3- phenalkyl, phenyl and alkylphenylthiazolidines, such as 3-benzyl, 3-phenyl and 3o-ethylphenylthiazolidine; 4,5- methyl and ethylthiazolidines, such as 4-methyl-, 4,5- dimethyl-, S-ethyland 4,5-diethylthiazolidine; and thiazolidines containing substituents in more than two positions, such as 2,2,4,5-tetramethyl-, 2,2-dimethyl-3- aminoethyl-, 2-phenyl-3-propyl-4-ethyl-, 2-methyl-2- benzyl-4,5 -diethyl-, 2-p tolyl-2-ethyl-3-hydroxyethyl-, and 2-pentamethylene-3-cyclohexyl-4,5- dimethylthiazolidine.

Of the thiazolidines described by the general formula above, those in which each R is hydrogen are preferred. Also preferred are those compounds wherein each R and R" is hydrogen or an alkyl of one to five carbon atoms. Especially preferred in the present invention is the use of 2,Z-dimethylthiazolidine, i.e., where each R and R are H and each R" is methyl in the general formula.

To obtain the improved cation exchange resin catalyst, the strong-acid resin is usually partially neutralized with the thiazolidine by direct neutralization of the free acid resin. The-degree of neutralization is readily verified by measuring the ion-exchange capacity of the resin before and after partial neutralization.

The extent of the neutralization of the catalyst of the thiazolidine may vary widely. About 5 to about 35 mole percent of the strong-acid groups of the cationexchange resin can be neutralized, with the neutralization of 15 to 25 mole percent of the strong-acid groups being preferred. As a general rule, neutralization of a high percentage of the exchange capacity impairs the efficiency of the catalyst in the preparation of bisphenols and should be avoided. Particularly effective cutalysts are obtained by neutralizing l5 to 20 percent of the cation-exchange capacity of a sulfonntcd aromatic resin having an initial exchange capacity of about 4.5 to 5.2 meq./g. dry weight H form giving a modified resin having a capacity of about 3.6 to 4.4 meq./g. dry weight H form.

The water content of the partially neutralized catalyst is an important process variable. Although some water is always present as a by-product of the phenolketone condensation, the catalyst efficiency is impaired lower temperatures, an inert diluent may be required to if the water content of the reaction mixture is greater than about 2-3 weight percent. A steady state water content of about 0.5-1.0 weight percent is preferred. When the modified resin is used in a fixed bed continuous reactor, the resin catalyst can be dried if necessary 5 by pretreating the resin bed with anhydrous phenol. Thereafter, the mole ratio and feed rates of the reactants can be adjusted to achieve a suitable conversion and eluent water content.

The partially neutralized cation-exchange resin of the invention is an effective catalyst for the preparation of many bisphenols. The phenolic reactant must be unsubstituted in the para position, but can be substituted with one or more alkyl, halo, or other similar nonreactive groups in the positions ortho and meta to the phenolic group. Suitable phenols include phenol, oand m-cresol, oand m-chlorophenol, o-bromophenol, o-sec.-butylphenol, o-t-butylphenol, 2,6- dibromophenol, 2,6-di-t-butylphenol, 6-chloro-ocresol, and o-phenylphenol.

As the ketone reactant, methyl ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone and acetophenone are preferred. However, cyclohexanone and other cyclic ketone as well as halo substituted methyl ketones like 1,3-dichloroacetone can also be used.

The preparation of bisphenols using the partially neutralized strong-acid cation-exchange resin as catalyst occurs readily under the normal conditions for the condensation of a phenol and ketone using a conventional cation-exchange resin or soluble catalyst. An excess of phenol is generally desirable to achieve a high conversion of the ketone. Thus from 2-25 moles of the phenol per mole of ketone are normally used with optimum conversions and efficiencies being obtained with a feed ratio of about 10-20 moles of phenol per mole of ketone.

The partially neutralized resin catalyst can be slurried with the reactants in a batch process or used in a conventional fixed bed column for continuous operation. The condensation in the presence of the modified catalyst occurs at temperatures ranging from 0 to 120C. and preferably at about 20 to 100C. at the maintain fluidity. Normally atmospheric pressure is used.

The reaction time of course depends on the reaction temperature and the method of operation. In a batch process, a reaction time of from 0.1 to 20 hours or more may be required to achieve a desired conversion. 1n continuous operation using a fixed bed of catalyst, a flow rate of about 0.2 to 6.0 bed volumes per hour or an average contact time of about 0.16 to 5.0 hours is suitable. Using a partially neutralized catalyst having a residual exchange capacity ofabout 3.2-4.5 meq./g. dry weight, optimum results are obtained with a feed rate of about 1.0 to 3.0 bed volumes per hour at -80C.

After separating the product mixture from the insoluble catalyst, the bisphenol is readily recovered by conventional means. Normally water, excess phenol, and other light impurities are removed by flash distillation. The residual crude bisphenol has a minimum purity of 10 percent, good color and is uncontaminated with residual catalyst or promoters. Additional purification by distillation, crystallization, solvent washing and similar techniques readily give a product having a purity of 99+ percent.

SPECIFIC EMBODIMENTS Example 1 Preparation of the Catalyst 2,500 Ml. of Dowex 50Wx8 (H") a sulfonic acid resin containing 4.95 meq/g. dry resin was washed with a volumetric excess of distilled water into a pot. To the water-resin slurry, 99.5 g. (0.85 mole) of 2,2- dimethylthiazolidine was added and the resin was stirred for 30 minutes. Excess water was decanted and the resin was then washed twice with fresh deionized water. To dry the product, the resin was slurried with excess phenol and the liquid was distilled at mm. Hg, and the azeotropic mixture of phenol and water was distilled until the temperature of the distillate reached 100C. The resin capacity before promotion was 4.95 meq./g. dry weight and after promotion was 3.97 meq./g. dry weight for a promotion of 20 percent.

Example 2 Use of Promoted Catalyst A stainless steel reactor column was charged with 630 m1. of the promoted resin prepared in Example 1, and a mixture of phenol and acetone was passed through the column. After steady state conditions were achieved for given reaction temperature and feed rate, samples of the product stream were analyzed. The bisphenol A analyses were obtained by stripping unreacted acetone and excess phenol from the reaction product and analyzing the residual crude bisphenol A for percent o,p'-bisphenol A by the vapor phase chromatographic methods described by Gill in Anal. Chem. 36, 1,201 (1964) and for color in methanol solution using a Klett colorimeter calibrated to standard American Public Health Association (APHA) scale. The conditions and results at various times after starting the run are shown in Table l. The product was of acceptable purity, 95 percent, after 5 hours of operation.

Comparative Example A TKTB'LE L-PTtEPARATION OF BISPHENO'L A USING A PROMOTED CATALYST Feed Acetone Bisphenol A Bun rate, converttme, bed sion, Wt., Percent, APHA hr. '1 C. vo1./h percent percent 1 o, p'- color Example:

1 In effluent.

In the same manner as described in Example 1, Dowex 50Wx8 (H resin was percent neutralized with Z-mercaptoethylamine hydrochloride according to U. S. Pat. No. 3,394,089. This promoted catalyst was then tested with the same feed as shown in Example 2, and the resultsof these tests are shown in Table l. The product was not of acceptable purity until after 12 In the same r n anner as shbwfiifi Example 1, strongacid cation-exchange resins may be promoted with 5-35 percent of 2-methyl-2-phenylthiazolidine, 2,2- (pentamethylene)thiazolidine, 2-methyl-2-carbethoxymethylthiazolidine, 2-methyl-2-dodecylthiazolidine, 2,2,4,5-tetramethylthiazolidine, 2,2,3- trimethylthiazolidine, 2,2-dimethyl3-octylthiazolidine or 2-methyl-2-ethyl-3-aminoethylthiazolidine. In the same manner as shown in Example 2, these promoted catalysts may be used to prepare bisphenol A or other bisphenols by the condensation of a phenol and a ketone.

We claim:

1. In the process for preparing a bisphenol by the condensation of a phenol and a ketone in the presence of a strong-acid catalyst, the improvement comprising using as the acid catalyst an insoluble strong-acid cation-exchange resin which has a cation-exchange capacity of at least 0.5 meqJg. and in which about 5 to about 35 mole percent of the strong-acid groups have been neutralized with an amine neutralizing agent consisting essentially of a thiazolidine of the general formula where each R is H, methyl or ethyl, each R is H, alkyl, hydroxyalkyl, cyanoalkyl, aminoalkyl, cycloalkyl, phenalkyl, phenyl or alkylphenyl of up to about 10 carbon atoms,

each R" is H, alkyl, cycloalkyl, phenalkyl, phenyl or the thiazolidine are H and each R" is methyl. 

2. The process of claim 1 wherein the phenolic reactant is phenol and the ketone is acetone.
 3. The process of claim 1 wherein the temperature is 0* to 120*C.
 4. The process of claim 1 wherein each R and R'' of the thiazolidine are H and each R'''' is methyl. 